摘要
碳同位素动力学是在生烃动力学基础上发展起来的方法。本文采用crammer模型,通过实验条件下对东濮凹陷沙河街组烃源岩进行生烃热模拟并用kinetics软件获得动力学参数,然后在excel的spreadsheet中完成拟合,并结合前梨园洼陷热史得到实际地质条件下前梨园洼陷天然气从生烃开始的累积碳同位素变化曲线和从28.4 Ma开始的阶段性累积曲线。前梨园洼陷是白庙地区的主要气源,结合白庙地区的天然气碳同位素范围?36.1‰~39.9‰ (PDB)在长期累积曲线上超过了最大值,而在阶段性累积曲线上落在27.5~25.5 Ma,认为前梨园洼陷生成的天然气是从28.4 Ma开始累积成藏并在27.5~25.5 Ma结束的。
Carbon isotope kinetics is developed from hydrocarbon generation kinetics. In this paper, cram-mer model is accepted and kinetic parameters are gained in kinetics software on the basis of thermal simulation experiment of kerogen from shahejie formation in Dongoingpu depression. Then an isotope kinetic model is established in spreadsheet to fit simulation result with experi-ment data in stable carbon isotope of natural gases. The variation in methane carbon isotope values under geological condition from the beginning of hydrocarbon generation and the other variation from 28.4 Ma are gained combined with burial history and thermal history in Qianliyuan depression. Qianliyuan depression is the main source of natural gas in Baimiao area, and the range of natural gas isotope in Baimiao is between ?36.1‰ and 39.9‰, bigger than the maximum of the variation from 44 Ma but is located in 27.5~25.5 Ma in the variation from 28.4 Ma. The natural gas generated in Qianliyuan depression is accumulated from 28.4 Ma and ended in 27.5~25.5 Ma.
